The invention relates to an air-conditioning system with a compressor, with an electric motor and with a refrigerant circuit, in particular for motor vehicles, the electric motor being controllable by means of an electronic control device and an expansion member (valve or orifice tube) being arranged in the coolant circuit.
For cooling the electronic control device in air-conditioning systems of the generic type, it is known from DE 199 25 744 to arrange the control device in such a way that the discharge of the lost heat takes place essentially via the refrigerant of the compression refrigerating system. In systems of this type, a cost-effective thermostatic expansion valve, with a statically permanently set wet-steam fraction, or an orifice tube is used in the refrigerant circuit. In this case, at many operating points, sufficient cooling is not ensured. At other operating points, in turn, the control device is cooled to a greater extent than is necessary, thus leading to marked losses of refrigerating capacity of the air-conditioning system.
The object of the present invention is to ensure sufficient cooling of the control device, while losses of refrigerating capacity are to be kept as low as possible.
This object is achieved, according to the invention, in that a further expansion member is arranged between the high-pressure side of the expansion member and the suction side of the compressor in the refrigerant circuit, to the low-pressure side of which the electronic control device is connected thermally conductively, and in that the further expansion member is controllable as a function of the temperature of the control device.
The air-conditioning system according to the invention ensures that the control device, in particular the power semiconductors, are cooled sufficiently for reliable operation, only a little cold being extracted from the refrigerant circuit and consequently a maximum cold quantity being available for air-conditioning purposes.
In an advantageous development of the air-conditioning system according to the invention, the further expansion member and preferably also the electronic control device are arranged within the housing of the compressor. In this case, the further expansion member delivers to the control device and, if appropriate, to the electric motor the refrigerant wet-steam quantity which is necessary for cooling. By virtue of this compact construction, additional contacts and lines to the on-board power supply can also be avoided.
Suitable actuating elements in the further expansion member are bimetals, expandable liquids, gases in capillary sensors and similar devices which open or close the valve passage cross section via a closing element as a function of the temperature of the control electronics.